Prof Hardwigg went in to see what the unknown holds in Jules Verne’s ‘A Journey to the Centre of the Earth’.

Years later, a robotic groundhog out here in Kolkata is digging out soil from the heart of the city. It is the tunnel boring machine used for the East-West Metro project.

The gigantic 80-metre long German machine, guzzles nearly 2,000 litres of diesel or 220 kVa of power to dig deep underground to create a 5 km-long cavernous tunnel.

The nearly 5-km stretch will come up after consuming nearly 2.5 lakh cubic metres of concrete, 45,000 tonnes of reinforced steel and nearly a lakh tonne of cement.

The tunnel will help the new 15-km tube-link connect between the IT hub in Salt Lake’s Sector V (on the eastern fringes) and Howrah Maidan (on the western flank of the river Hooghly).

The underground part will pass through some of the busiest parts of the city including the Howrah and Sealdah stations. As we watch, the machine keeps burrowing, taking out tonnes of earth piling them onto a train.

Once burrowing is over, a robotic arm moves in with a concrete segments and places a 1.2-m wide pre-cast concrete ring.

A 12-metre length of the tunnel is thus created everyday.

Nearly 240 workers of the Indo-Thai consortium of ITD-ITD Cem sweat it out.

Around 20 per cent or 48 of them are of Thai origin specialised in such tunnelling.

Normal Life Unaffected

As work goes on in full flow nearly 1.8 metres below the road surface, traffic movement and normal life atop is unperturbed. Building residents take a look at the ongoing work from their multi-storied apartments - some in wonder and some unhappy with the dust generated.

“I remember life was thrown out of gear when the north south metro line came up. Initial years, were tough on the common man,” Mr Anil Khurana, a resident of the region said.

ITD - ITD Cem officials admit that except the diversion and some closure of roads there have been very less disruptions.

Monitoring of work

“We surveyed the underground utilities and nearby buildings where work will take place. We have been careful in measuring vibrations to see if damages have been there or not,” Mr Chundee Mookhan, Project Manager (Tunnel), ITD-ITD Cem, told Business Line. “We have been careful to see that there are no major disturbances,” he adds. He is not wrong. Down there in the tunnel, eyes are glued to a computers screen that monitors earth pressure.

Officials say that the TBM is aligned up to 4 mm accuracy and has been able to bore nearly 1.5 km (740 metres on up and down lines) with a speed 300 m per month.

(This article was published on June 26, 2012)
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